Hi half as many adults as there are children. Let x = Adults & 2x Children 5(2x) + 7(145-3x) + 12x = 1040 x = 1040 - 7*145 x = 25, the number of Adults, 50 children & 70 Students$5*50 + $7*70 + $12*25 = $1040 checks Wish You the Best in your Studies.